A rubber bearing which is comprised of a rubber member and a reinforcing member is used in supporting a structure such as a building and the like. As a result of the fact that such rubber bearings are generally disposed in a lower portion of the structure, the rubber bearings receive the load of the structure over a long period of time, and are also subjected to shear stress due to earthquakes and the like, while they gradually deteriorate due to aging or the like. When the deterioration of a fixed level or more has occurred, it is necessary to replace the rubber bearings, and the extent of the deterioration of the rubber member of the rubber bearing is conventionally ascertained by visual observation of a configuration or dimensional change in the overall configuration of the rubber member, a crack or an exfoliation in the rubber member or the like, or by the use of a measuring instrument such as a strain gauge, an ultrasonic test instrument, or a measure.
Since the rubber bearings are generally disposed in a lower portion of the structure as described above, the visual observation of the rubber members is very difficult since an inspector must enter the lower portion of the structure and conduct the visual observation. In addition, the inspector must rely on his experience and intuition in the observation, so that there is a possibility that the results of observation may vary. Meanwhile, in the observation of the rubber members by the use of measuring instruments such as those described above, it is possible to obtain satisfactory results to a certain extent when a dimensional change is involved. When a dimensional change is not involved, it is impossible to obtain desired results. In order to monitor the supporting performance of the rubber bearings during the period of use, it is necessary to remove the rubber bearings from the structure, or separately prepare in advance a rubber bearing specimen of the same material as that of the rubber bearings installed under the structure, and to conduct a dynamic test by applying a fixed axial force to the rubber bearing specimen after the lapse of a predetermined period. Thus, it has been impossible to monitor the supporting performance of the rubber bearings in use as installed under the structure.
Such a problem occurs not only with the rubber member itself of the rubber bearing, but, generally speaking, it can similarly occur with rubber members applied to various members which are formed of material such as natural rubber, synthetic rubber, or the like.
The present invention has been devised in view of the above-described aspects, and its object is to provide a method of detecting a change in the property of a rubber member, the method being capable of reliably observing the extent of deterioration even when a dimensional change is not involved, and in the case of a rubber member of a rubber bearing, making it unnecessary for an inspector to enter a lower portion of a structure at the time of observation, and making it possible to reliably ascertain the extent of deterioration remotely.